


Gaster Does Not Like

by idontevenknowugh



Category: Undertale (Video Game)
Genre: Come Inflation, Come as Lube, Gangbang, Jealousy, Large Cock, M/M, Multi, Painful Sex, Power Dynamics, Public Use, Punishment, Rape/Non-con Elements, Sanster, Sexual Exhaustion, Stepped On, kingdings
Language: English
Status: Completed
Published: 2018-09-01
Updated: 2018-09-01
Packaged: 2019-07-05 06:30:05
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 1
Words: 4,078
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15858123
Author URL: https://archiveofourown.org/users/idontevenknowugh/pseuds/idontevenknowugh
Summary: Gaster is smart, very smart, but also so very dumb. He should have known the King was a jealous man, even over that which was never really his.





	Gaster Does Not Like

**Author's Note:**

> Purr suggested that I should just use my working titles and nothing was coming to me, so...
> 
> This was the result of a conversation with undertailsoulsex about inflation and Kingdings and gang bangs. And I just really liked the idea a lot. >_> I hope you do, too.
> 
> There’s a cameo from Lycovore‘s OC, Spot in there, too, just for giggles.

Gaster’s steps slowed as he neared the throne room. He didn’t mean to dawdle. Wasting time was something he would never condone, but Asgore’s summons were sometimes…

No matter how slow he got, he would eventually reach the door. Maybe if he was Zeno, he would imagine that there was a speed at which he could never cross that final half, but he knew better. He picked up his pace to the normal sharp steps that warned his staff he was near.

The door opened before his long strides reached it, however, pushed out by a surly looking guard. Gaster had no interest in the King’s meat head military. He had probably seen this one before- on the way to the King’s bed?- but he had no idea what the monster’s name might be.

“Get in there,” the guard nodded in the direction of the throne. Clearly, he knew who Gaster was. That, however, only made sense. He was the royal scientist. Voices, too quiet to be understood, filtered out into the hallway, and Gaster relaxed. If others had been summoned as well, he was safe. For today.

Rather than dignify the gruff command from the lesser monster, Gaster tilted his skull up and put on his most haughty expression as he walked through the doors.

The group of monsters he had heard was scattered around the room, gathered into clumps of three or four. Asgore towered over one group, chatting in a low voice. His back was to Gaster, which was just fine with him. Tables with trays of food and pitchers of drink surrounded the throne, giving the whole event a party-like feel.

Another lab coat stood out amongst the fine clothes and polished armor of the other guests. Gaster’s soul felt heavy, though he wasn’t quite certain why. He should be happy to see Sans. Seeing Sans was always the best part of his day. However… why was Sans here?

“doctor gaster!” Sans brightened at the sight of him. He had been listening to some whimsalot drone on about the security measures being taken around the core. Gaster had been forced to attend some of the meetings for that initiative and could confirm that it was the most boring topic in existence.

“Sans,” Gaster greeted his assistant warily. The dread that had hooked into his soul wasn’t letting up. There was something wrong about this whole situation. He hadn’t even been told why he had been summoned. If the King wanted him to shmooze, he could have at least warned him.

“Oh good, you’ve made it, Doctor!” Something had grabbed Asgore’s attention, unfortunately. His voice boomed as he greeted Gaster, halting all the rest of the conversations and drawing attention to them. Gaster flushed a little at the sudden scrutiny. Even Sans looked around nervously, quickly taking a few steps back out of the way.

“Your Majesty,” Gaster greeted him, bones prickling with the urge to flee.

“Come, come,” Asgore walked up to him and set a large hand on his back. Gaster shivered where it landed, memories of those hands unwelcome but persistent. Asgore steered him towards the throne. He stopped when they were near the center of the group, in front of one of the tables. With entirely too much force, Asgore turned, pushing Gaster with him quickly enough that he stumbled. Collecting himself, he looked out at the other monsters.

They had collected in a semi circle around that side of the throne, all eyes on them. Gaster hunched into his lab coat a little, feeling self conscious.

“Everyone, thank you for joining us today! Now that the esteemed doctor has arrived, we can get started.” His hand curled slightly against Gaster’s back, his claws digging into his coat. He could feel one against his spine, pricking the bone lightly. Sans was watching from one side with open curiosity.

“Enjoy,” Asgore growled, his hand pressing forward with sudden force. Gaster fell forward onto his knees, the hard tile floor bruising them painfully. He didn’t understand what was happening. The monsters were getting closer, wicked grins across the faces he could see.

“doctor gaster!” Sans called out from somewhere. Gaster couldn’t see him anymore. He sounded upset, panicked. Gaster tried to get to his feet, but Asgore’s hand fell onto his shoulders, keeping him down.

“Sans?” Gaster knew he shouldn’t, but he was getting worried. He knew damn well he shouldn’t show the least bit of concern in front of the King. Weakness was never a good idea, but especially not with Asgore. Especially not about Sans.

“Don’t worry, doctor,” Asgore’s breath was hot on his skull as he ‘whispered’ against it in a dull roar. “They’ll make sure he’s taken care of, and these fine monsters will help sate you. Since you clearly want for more partners.”

“W-what?” Gaster stuttered. He looked up into Asgore’s red eyes and found them narrowed with anger. His brain, which had not possessed all the pieces needed, could now solve the puzzle. Asgore knew. He had found out, and this was the result.

And Sans was caught up in it.

“No, stop,” Gaster gasped. Someone grabbed his arm, pulling him forward. He leaned back, keeping his spot under Asgore’s hand. “Let him go.”

Asgore growled, the sound echoing around the chamber. Everything stopped, though the monster didn’t let go of Gaster’s hand, just ceased pulling. Somewhere behind the mass of bodies was the sound of struggling and muffled words.

“You should have thought harder before giving him what is mine, doctor. I imagine this will ensure there’s no such transgression in the future.” Asgore removed his hand and stepped back. “Go on, my friends,” he announced.

The monsters crowded around Gaster. It wasn’t just his arm now. Hands pulled at his lab coat, trying to peel it off of him. Someone was pawing at his pants, trying to unfasten them. Another monster couldn’t be bothered to wait and licked a large stripe up the side of his skull.

“Stop,” Gaster snapped, summoning several more hands to take hold of his clothes and keep them in place. They, of course, didn’t. If anything, they got more insistent. His coat felt like it might tear.

He started to summon bullets to strike them with, bones with sharp, needle-like points. Before he could send them out to the rabble, Asgore’s large hand waved absently through them. They crumbled, destroyed with all the effort necessary to banish a fly.

“Now, Doctor,” Asgore's rumbled, and Gaster was pulled against his chest. The king’s armor made an uncomfortable surface, pressing against Gaster’s processes painfully. It was still preferable to Asgore’s bare chest. “I thought you understood the value of recognizing cause and effect.

“This,” he grabbed the front of Gaster’s shirt with one large hand, crushing several of Gaster’s extra ones in the process, “is the effect born of your behavior.” Asgore pulled. For a moment the sweater held on, cutting painfully into his cervical vertebrae. It gave, however, and the entire front panel went, leaving Gaster’s ribs uncovered.

Gaster had a sudden urge to cover himself, but he already knew it was futile. There was no going against a boss monster when they were calm, and Asgore was pissed off. He wasted no time in repeating the violence to Gaster’s pants, ripping out the front so they slid down his femurs.

Now that he was properly on display, Asgore changed his grip. His arms wrapped under Gaster’s shoulders and back up, curling towards himself. Gaster was left without the ability to move his arms. Then Asgore’s knee pushed Gaster’s pelvis forward. It went, helpless before the raw strength.

_Now_ he was properly on display.

The other monsters hollered and laughed, surging forward. Gaster flinched away from their reaching appendages, but he was fixed in place. There was nowhere to go. Surely Asgore wouldn't want to hold him for the entire event. Just long enough for them to drain the fight out of him. Gaster wouldn’t get the chance to make an escape. Asgore was too talented a tactician to give him an out.

Red magic flared up behind the monsters. Sans! Gaster had almost forgotten about him. He struggled a little more, trying to see.

“Oh, so you like them spunky,” Asgore laughed. He was a full head taller than Gaster, and could see over the crowd. His delighted expression did not speak well for Sans’s chances. Sure enough, there was a strangled cry, and the magic died down.

“Oh well,” Asgore muttered as a monster pressed its body against Gaster and started to hump him. He didn't catch the monster’s variety before his sockets were filled, literally, with squishy blue flesh. He could only recoil a few centimeters, which didn't help. They had a cock, which he could tell was hard as it rubbed along the front of his pelvis.

The other monsters kept touching him, for some reason. There couldn't have been any pleasure in doing so. Unless they enjoyed making him uncomfortable. Oh, that was probably it. Something small climbed up his left leg, squeezing past his assailant and into his rib cage. He lost track of it there, which was incredibly worrying.

It was quite distracting having the monster in front of him, however. They were speeding up, the friction of their cock against his bone a little painful. The sensation was also, unfortunately, fairly pleasurable. Magic seeped into his pelvis, warming it. When the monster came, splattering it's rapidly cooling cum all over the inside of Gaster’s lower rib cage, he shivered. It withdrew, or was pulled away by the next eager participant.

“Enjoying yourself, Doctor?” Asgore rumbled with a laugh. Gaster grimaced at the idea that this humiliation could ever be desirable. The next monster seemed to be annoyed by Gaster’s lack of preparation. It poked at his pelvis in a barely arousing way.

“Stop going easy on him,” Asgore growled, releasing one of his arms and shoving the monster away hard enough that they fell. Others filled the gap. Gaster couldn’t see what became of them. Asgore didn’t care, clearly, because he went straight to rubbing along Gaster’s pelvis. He had learned, from experience, what worked for skeletons, and he brought it to bear now. Each touch was a calculated move to make his magic form, and they worked disturbingly well.

Gaster’s genitalia never quite behaved like Asgore wanted, but the king had figured out how to force it into the shape he desired. As it was still forming, he shoved three fingers up into Gaster’s pelvic inlet, blocking the magic there. Gaster’s magic, resistant to forming incomplete parts like that- Gaster had run some experiments to see if he could halt this process- formed into a pussy around them.

Barely waiting for it to finish, Asgore pulled the fingers out, thrusting them into him a few times. This caused an unfortunate slickness as Gaster’s body tried to ease the painful friction. It didn't help much, but the fur stopped catching on the walls.

“Alright,” Asgore withdrew them too quickly and waved his arm out, splattering several monsters with Gaster’s arousal, “Next!”

A burly bull monster shoved the others out of his way to stand in front of Gaster. His pants were straining to contain his bulge, but it's suffering was short lived. Gaster's was just starting.

The monster’s cock fell down, heavy, thick, and long. It was so long that, despite clearly being erect, it curved down towards the floor, it's tip flaring wide. That alone looked too big to fit into Gaster’s magic. He knew it could, thanks to the King- who was wider, but much shorter. Unfortunately, that meant Gaster would be stuck dealing with the rest of it.

Asgore rumbled unhappily, but held onto Gaster as the bull gripped his cock and aimed it as Gaster’s barely prepared magic. Was his majesty feeling inadequate? Gaster would have enjoyed that, if the lips of his pussy weren't being forced apart by the thing. He tensed, even though he knew that it would hurt more. He had never mastered the baser instincts- fear… love-  like he should have. If he was as cold as he always pretended, maybe this wouldn't have happened. He would be here, and Sans…

Gaster hadn't heard him cry out in a while.

Sans was wiped from his mind so he could focus on the feeling of being split open. His magic strained against the intrusion. It was too thick and it was far, far too long. Only a third fit, but the bull continued to try, pressing the tip painfully against the back of Gaster’s vagina.

“Ouch, fuck, stop, you imbe- ah! Imbecile!” Gaster gasped, wriggling in Asgore’s hold. “There isn't anywhere to put it!” The bull stopped, but only to look annoyed. Hot air blew out of his nostrils and washed over Gaster’s skull.

“Let’s not be too hasty,” Asgore interjected. “You are quite proud of your magical control, Doctor.”

“That's- ngh- different,” Gaster panted. Tears pricked at his sockets. Stupid physical responses to pain.

“Is it, though?” Asgore asked and pushed Gaster’s pelvis forward, increasing the pressure even more.

“Ahhh!” Gaster cried out, struggling harder. It was going to rip. The magic would give much sooner than Asgore would.

“Okay, Okay!” He shouted. He desperately reshaped his magic, extending it and widening it when it got past his pelvis. As it grew, the bull’s member slipped deeper inside. Gaster didn't stop until the pressure against the back eased, at which point the head had reached the bottom of his ribs.

The only tightness left was where the bull’s cock was squeezing through his pelvic inlet. As uncomfortable as that was, it was better without the rest of the pain. The bull seemed satisfied enough. He started to thrust, long powerful movements that jarred Gaster’s body as the monsters muscular hips hit his pelvis. Asgore made a few more disgruntled noises as he watched the huge thing leave and then fill the magic. Unfortunately, he never got jealous enough to stop it.

Gaster's relief didn't last. The rough thrusts aggravated the magic and even strained the bones. It got worse as the bull got close, his movements more erratic and careless.

He released inside Gaster with a series of hot huffing snorts. As he did so, he leaned forward, as if there was any deeper to go, his face far too close. A long tongue hung from his mouth. Thankfully he didn't try to kiss Gaster, but saliva dripped down from it onto his skull. It was hot and slimy, sliding down the bone and making wet trails alongside the tears he hadn't been able to stop.

The flood of release was pushing his magic out again, seemingly never ending. When it finally did abate and the bull pulled out, the cum remained. He wanted it out. Out. Out!

“Why Doctor,” Asgore laughed, “I didn't realize you were so hungry for their cum that you would make a place to store it.” He pat what was now a swollen sack of magic. “I'm sure you're quite ready to hold onto the rest of our visitors’ as well.”

The threat was unmistakable. Gaster wondered what he would win by doing it. Was there anything he had yet to lose aside from his life? It's value was currently debatable.

He still hadn't heard Sans.

“Of course…” Gaster agreed miserably. Asgore rumbled his approval before raising his already loud voice to speak over the excitement of the gathered monsters.

“Doctor Gaster, slut that he is, is begging for more cum. Who would like to be the next to oblige him?”

There was a rush at that. Monsters shoved and shouted, waving their dicks around to try and get them into him first. Surprisingly, a skinny little monster with long, spider-like fingers won out. Compared to the bull, his cock was nearly nonexistent, but he laid his body across Gaster's and humped him rapidly with small, sharp movements.

It was annoying up until he released more cum into Gaster. The _royal scientist_ trembled, disgusted by the smell of sex and sweat, the sloshing of the liquid inside his magic. It was already close to full. To make sure he didn't disobey Asgore, Gaster widened the sack. It settled into the top of his pelvis, heavy and percarious.

As the monster was yanked out of the way with a yelp, a rabbit monster, of all things, elbowed his way in to take his place. Gaster braced himself. The reputation of rabbits’ mating drives was… disturbing. The rabbit pulled open his pants and thrust into Gaster, immediately setting a brutal pace that hardly felt like separate movements. Gaster could only tell that he was thrusting and not somehow vibrating because his pelvis started to feel sore from the repeated impact.

Thankfully, the rabbit was just as quick to finish. He didn’t pull out, though, and Gaster didn’t feel him soften. He merely paused and leaned forward. His mouth opened and Gaster had a horrible moment of thinking the monster wanted to kiss him, but he bit down on his clavicle instead.

“Fuck!” Gaster swore from the the pain, but he was actually relieved not to have to participate in anything resembling affection with the rabbit. Or any of them. The rabbit nibbled at the bone for an extended moment before the crowd got impatient and dragged him away.

The next offender was a bird monster that squawked with every thrust and then trumpeted his release with a long crow of what Gaster had to assume was pleasure.

When the following monster stepped up to him, he snuffed out his eyelights. Seeing the monsters did nothing but sicken him further. They were willing pawns in Agores little revenge play, and all so they could stick their dicks somewhere. Pathetic bastards. They would never have been able to get the best of him or Sans without the King’s help.

Where was Sans?

He didn't have much of a chance to try and find out. The monsters kept coming, each one adding to the revolting soup in his magic. Repeatedly, he felt the magic strain under the contents and had to extend it, but there was only so far he could go with his genitalia. The magic wasn't meant to be used this way. Eventually, Asgore grew tired of holding him and passed him over to the monster using him. Gaster had simply ended up on the floor.

He finally ran out of magic to grow the sack, despite how it bulged out from his pelvis. Yet another hot, vile release joined the rest, and, when the monster withdrew, Gaster had to clench the magic to keep it all inside. Why was he doing that? He could only hope it was enough.

For once, no one mounted him. Gaster was struck by how strange it felt to not be grabbed and fucked. How many times had it taken for the lack of abuse to stand out so strongly? Tentatively, he brought his eyelights back.

The monsters were filing out of the throne room, laughing and chattering. Asgore alone remained, his very presence powerful. Gasping with the realization that it was actually over, Gaster rolled his skull around, looking for Sans.

A few feet away- so close- he found a crumpled form, lab coat torn and cum dripping down his skull. With trembling limbs, Gaster rolled over and got onto his hands and knees. The bulbous pouch jiggled, a little of the mixture slipping out to run down his femur. What did it matter.

Was Sans injured?

He wasn't moving.

His HP-

“Oh Doctor, I thought you were supposed to be smart,” Asgore sighed from directly above him. He shouldn't have been able to sneak up on Gaster, but he was panicking, blind to anything but checking on Sans.

A large hand reached under Gaster and cupped the distended magic. He couldn't continue on with it there, so he froze. Massaging motions strained his ability to hold onto the cum. Asgore had told him to do it, and Sans was right there. He wasn't dust. Gaster couldn't protect him, aside from trying to appease the king. It didn't matter how hard he tried, however. Asgore’s touch forced more from him, the drip becoming a dribble.

Two loud thumps were all the warning he got before Asgore took him from behind. Gaster groaned with pain as magic that had been brutalized was forced to accommodate the king’s oversized member. He had trouble with the thing normally, let alone after- hours?- of use.

Gaster hadn't been anywhere near aroused for quite a while. The only thing easing the way anymore was cum. It turned out that it was not all that effective of a lubricant. Not when it was trying to smooth the movement of something so ill fitting. Wracked with pain, all Gaster could do was brace himself on his elbows and keep an eye on Sans as his body swayed from the King’s graceless thrusting.

That turned out to be too much effort, as the fucking drew out. Gaster tried, he really did, but he bowed his skull and let it rest on the ground behind his hands. He didn't even feel upset anymore, just weary. His sockets prickled again, but he was all out of tears. His feelings were as impotent as his power in this world. He had thought he was brilliant, mighty, and vicious enough to survive this hellish place. He had been so devastatingly wrong.

Asgore began to grunt and bleat. Of course he had wanted everyone gone before taking his turn. Gaster had laughed the first time, driving the King into a rage.

Gaster had told Sans that he'd lost that floating rib in a fight.

At least it meant he was almost done. Gaster repeated the thought like a mantra to keep his exhausted body from simply passing out. Who knew what the fuck Asgore would do to them if they were both unconscious.

Finally, Asgore stiffened above him and began to release. While he was not as virile as the bull, he well out produced the rest of the monsters. There was no chance that it could be contained, so it squeezed past his cock to join what had already made a mess of Gaster’s femurs.

“Ah,” Asgore sighed and extracted himself. A glob of cum followed him, splattering onto the ground, before Gaster was able to stop the flow. Holding it back was getting painful.

“I do hope today has been educational, Doctor,” the King grunted as he stood back up. Fabric rusting and metal clinking filled the silence following his words. Educational?

Gaster looked back up at Sans. Still not dust, but also unmoving. Quickly, he looked away. Oh yes, he had learned plenty. Slowly, he let himself sink to the ground. He was laying on his magic, which was both uncomfortable and liable to make him lose control. Demanding a little more from his limbs, he rolled over again, to lay on his spine.

“I expect you to take all of your duties to the crown seriously from here on out.”

Asgore’s final warning was accompanied by a sharp grin and a raised foot. Gaster was too worn down to figure out what he was planning until it was already underway. The King’s hard boot came down slowly onto Gaster’s bulging magic. Gaster groaned and tried to hold on, but nothing could stop the strength of the King.

First a trickle, then a stream, and finally a flood of cum rushed forth from Gaster’s pussy. It splashed across the floor and spread so that he was laying in a pool of it. His body found some tears to shed over the pain and humiliation of it. The process seemed to take forever. Once he was empty, Asgore removed his foot, careful not to step in the mess. Gaster’s magic had collapsed in on itself. It was draped over his spine, saggy and still lined with a coating of cum.

Asgore eyed Gaster with a cruel look. He pulled his cloak around him and walked towards the door to his private gardens.

“I’ll leave you two lovers to talk. I'm sure there's much you need to discuss.” He laughed, cold and harsh. Gaster dreaded what he would see, but he looked at Sans anyways. He was still prone, but shaking now. Conscious. Listening.

“See you tomorrow, Doctor.”

**Author's Note:**

> My tumblr is where I: take requests, post streams, chit chat, do teasers, try out new fics, reblog a lot of skeleton porn, pimp all my favorite fics


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